The rod inside the rebound spring is a trigger stop. The factory installed some of those in N frames but they were smooth. They were factory installed in target sighted N frames during the 1970s and 80s and probably earlier. A lot of them were tossed out by owners who did not know what they were so it is hard to say how many revolvers got them.

The hand spring is a wire V spring inside the trigger. One leg of it has to be held up with something like a small fat head screw driver while the hand is installed.

Edit to correct myself. That piece cut off a bolt appears to be to large in diameter to slip inside the rebound spring. Apparently it is there to make up for over shortening the rebound spring.

I like Wolff's rebound spring pack that includes a variety of springs. While their 13 pound spring will not move the rebound slide back fast enough to keep up with Jerry Miculek it's the one I use most often. If I recall correctly the pack includes spring weights of 12 pounds through 15 pounds. A lighter rebound spring makes a big difference in the double action pull.